Heat-treating furnace



Feb. 10, 1931. R. COCHRAN 1,192,074

HEAT TREATING FURNACE Filed Oct. 5. 1928 2 Sheets-Sheet- 1 [1v VENTara.-

RS. CULT/{RAN ATTURNE Feb. 10, R a CQCHRAN HEAT TREATING FURNACE FiledOct. 3. 1928 2 Sheets-Sheet 2 INVENT'DR; CUC'HRAN' ATTORNEY PatentedFeb. 10, 1931 UNITED STATES PATENT OFFICE 4 RAID]? SMYTH COCHRAN, OFTOLEDO, OHIO, ASSIGNOR TO THE SURFACE COMBUSTION ('20., INCORPORATED, OFTOLEDO, OHIO, A CORPORATION OF NEW YORK HEAT-TREATING FURNACEApplication filed October 3, 1928. Serial No. 310,031.

This invention relates'to furnaces for heattreating relatively flatobjects such as sheet steel and has among its objects to provide aninterfingered conveyer of such form and construction that the sheetresting on the conveyer can be heated on its under side by gases ofcombustion from burners firing crosswise of the direction of travel ofthe sheets and to provide ways and means for preventing the unsupportedside edges of the sheet from sagging.

The above and other objects of the invention will more fully appear fromthe detailed description taken in connection with theaccompanyingdrawings forming part of this specification. r I

.Referring to the drawings:

i Fig. 1 is a side elevation of a portion ofa heat-treating furnaceembodying my improvements, parts being broken away to more fully showthe construction;

Fig; '2 is a more orflless diagrammatic sectional lan view on a reducedscale of the lower portlon of the furnace shown in Fig. 1

Fig. 3 isa-- transverse vertical section through the furnace shown inFlg. 1;

Fig. 4 is a fragmentary vertical/ section on an enlarged scale of theconstructlon shown in Fig. 3;

Fig. 5' is a fragmentary plan viewshowmg the relative position assumedby the adjacent relatively movable conveyer bars when they are in suchposition that the burden of the work or sheets is about to betransferred from one set of bars to the other; and

Fig. 6 is a side elevation of one of the elements forming part of eachconveyer bar.

The furnace is of tunnel form with substantially continuous side walls10and roof 11' and with end openings E through which the material to beheat-treated is advanced to'and from'the furnace'chamber. A horizontallyextending series of openings in the sidewalls allow for the positioningof gas burners 12 and 12 of any approved type but preferably of a typeadapted to burn explo-.

v 'sive gaseous mixtures. There is no stack, the

spntiproducts of combustion finding egress through the end openings E.

Thel'hearth of the furnace is a conveyer which consistsof two sets oflongitudinally drawings, the set of bars 13 is elevated, that is to sayin sheet supporting position, a sheet being indicated at S. It will beunderstood that when in such sheet-supporting position; the bars areadvancing, that is they are moving longitudinally within thefurnace-chamher in the direction from intake to discharge.- After theadvancing bars 13 have carried the sheets forward through apredetermined distance, the relative vertical movement between the twosets brings the bars to a level with the bars 14.1 The bars '13 thendescend and the bars 14 take the bur-den ofthe sheets. The bars 13,whenthey have come to a relatively lower position, recede, and afterrecession rise again to take the burden of the sheets and to carry themagain forward. The cyclic motion of the two sets of bars is identical. I

Each of the bars 13 and 14 is relatively high as compared with its widthand each bar is provided with a longitudinally extending seriesoftransversely extending similar ports or openings13' and 14:respectively. The ports or bars 13 are in alinementv as are also theports of bars 14 and the height and length of the ports of each set ofbars are preferably such that regardless of the relav tive positionbetween the two sets of bars, there may be an open passage through theports from one side ofthe furnace to. the other. For convenience ofdescription the series of communicating ports may be termed a bank ofports. Each bank of ports has its gas burner 12 (12') the burner. beingso positionedas'to fire ina direction through the ports from one side ofthe furnace toward the other. The burners in one wall are staggered withrespect to the burners in the opposite wall andhence the hot gases flowin opposite directions through adjacent port banks. During relativevertical reciprocation between the two sets of bars 13 and 14, the underside of the sheet S above the relatively lower set of bars will beexposed to the direct action of the hot gases. As shown in Fig. 4, someof the hot gases flow through the ports of the relatively lower bars andsome flow over the tops thereof as a consequence of which the tops ofthe lowered bars Will'become thoroughly heated. As a consequence of ibeing thoroughly .heated while out of contact with the sheets, coldspots on the sheets will not be formed when the bars again take theburden of the sheets.

The inner face of each furnace side wall is provided with alongitudinally extending in cut or reentrant portion from a pointadjacent the burners to a point above the highest level of the conveyerbars. For convenience ofv description one of these incuts is indicatedlevel in. the opposite side wall is a burner (15) adapted to dischargefresh combustion products above the conveyer members and towards thewall in which the burners 12 (12) are positioned. The combustionproducts discharged from burners 12 (12) set up an entraining effect infront of the entrance to the port banks. Due to this entraining effect,the combustion products from the opposite burners 15 15) after strikingthe wall wherein the burners 12 (12) are positioned tend to be drawnthrough the port banks into which the burners 12 (12) fire. The hotgases from burners 12 (12) are therefore tempered by the relativelycooler entrained combustion products with a consequent more uniformtemperature from one side to the other of the conveyer. The spent gasesleaving the port banks tend to mix with the fresh hot combustion gasesfrom the upper adjacent burners and therefore also temper them.

The top surface of the conveyer bars is preferably undulating in thedirection of-the length of the bars as indicated by numeral 16, theundulations of the respective bars of a given set being in transversealinement. By providing an undulatory sheet-supporting surface on thebars, the sheets tend to assume a corresponding undulatory form whilesupported on the bars. As is well known, a corrugated or undulatorysheet offers more resistance to bending on a line at right angles to thecoi'rugations than a flat sheet. The advantage of imparting anundulatorv form to the sheets as they pass through the furnace chamberwill be readily appreciated from the following description. If anunsupported side portion of the sheet S should sag there is danger ofsuch portion becoming wedged between the bars as for example byprojecting into a port opening 13 (14) adjacent the bar on which thesheet is supported or by wiping the side of the adjacent bar as theburden of the sheet is transferred from one set of bars to another. Bygiving an undulatory or corrugated form to the sheets any tendency ofthe sheets to sag and become wedged between the bars will be effectuallyprevented since the surface of corrugated form offers resistance tobending as will now be readily understood.

Another important result. obtained by stiffcning the sheets as aforesaidis that lateral displacement of the sheets on the bars is prevented; Forexample, if the sheet were not stiffened and an unsupported side portionthereof should sag and abut an adjacent relatively movable bar, said barwould tend to push or pull thesheetas the case may be and thus causesliding movement of the sheet on the supporting bar s. Such slidingmovement tends to scratch the sheets and thus to injure them for certainclasses of work. The un- 'dulations in thctop surface of the barstherefore serve "a's' mean s for preventing relative lateral slidingmovement between the sheets and the supporting bars.-

The undulations in one set of bars are so arranged with respect to thosein the other set that when both sets are in a common plane,that is whenthe burden of the work or sheets is being transferred from one of saidsets to the other,-the undulations of one set will be transverselyalined with the undulations in the other set as illustrated'in Fig. 5.By arranging the undulations as aforesaid, repeated flexing of the sheetis prevented as it is transferred from one set of bars to the other.Relative sliding movement between the sheet and the conveyor bars istherefore prevented with consequent elimination of any tendency ofscratching of the sheet due to such movement.

Each bar 13 (14:) is a composite structure and comprises alongitudinally extending base rail 17 (17) on which is mounted'a seriesof individual refractory rectangular blocks 18, the ports 13 (14) beingformed one in each block as clearly shown in Fig. 6. The adjacent endsof the blocks are preferably of tongue and groove construction asindicated at 1 9 in Fig. 5. The top surface of the blocks is undulatoryand forms the undulatory surface already referred to and may be cappedby a metal cap 20 as indicated in Fig. 4. It is preferred to provideheat-insulating material between the rails and blocks as indicated at21, the blocks and insulation being maintained against lateraldisplacement with respect to its' bar in an} suitable manner as by beingseated in a U- shaped saddle 22 which is secured to the rail 17. Inorder to reduce, to a minimum any 35 rups 27 and 27', respectively, inthe bottom the adjacent bars 13 and 14, there is-pro- 'vided in one sideof the bars a longitudinally extending and laterally projecting frictionmember 23 composed of a refractory material. This member may be insetinto the blocks 18 as shown.

The two sets of bars 13 and 14 may be supported for relative movement inany suitable manner. In the construction shown, the bars 13 and 14 aresupported on a series of cross beams generally indicated by numerals 24and 25 .respectively. In order to provide the necessary clearancebetween one set of rails and the cross'beams for the other set of rails,there is provided spacer blocks for supporting the rails in a planeabove their supporting beams. The spacer blocks between the cross beams24 and their rails 17 are indicated' at 24 and between the cross beams25 and their rails 17' at 25'. As shown the blocks are short pieces, onefor each rail andof the same cross section as the cross beams on whichthey rest. At intervals between the cross beams 24 and 25 are shortercross beams 24 and 25 which terminate short of the side walls of thefurnace chamber. The number of cross beams will of course depend on thelength of the furnace.

The cross beams 24 and 25 extend through the side walls of the furnacechamber, the walls being provided with arched'openings 26 for thatpurpose. The outer ends of the beams 24 and 25 are seated in individualstirof each of which is a knife edge bearing 28 on which-the beams rest.Each stirrup is secured to the lower end of an upright hanger 29 (29')the upper end of which is pivotally connected to crank arm 30 (30)secured to a shaft 31 (31); These shafts are suitably secured intheupper ends of upright standards 32 which also serve as buckstays forthe furnace walls.

Fixed to each shaft 31 (31) is crank arm 34 (34') and connecting thesearms is a link 35 (35). To the end of one of the crank arms 30 is alsoconnected a pitman 36 which leads to operating mechanism to be presentlydescribed. Aflixed to one of the shafts 31 is a crank arm 37 andconnected with this arm is a pitman 38. The lower end of the pitman 38connects with onearm 39 of 'a bell crank lever rotatably secured on asuitably supported shaft 40. The other arm 41 of said bell crank carriesa roller which rides on a cam 42 fixedly secured to a power shaft 43which'is driven in any suitable manner, not shown. The lower end ofpitman 36 connects with one arm 44 of a bell crank rotatably secured toa suitably supported shaft 45.. The other arm 46 of the bell crankcarries a roller which rides on the previously mentioned cam 42 at apoint diametrically opposite the roller bars 13 and 14 as will now bereadily under stood. 1

The means for imparting, relative horizon tal movement between the sheetsupporting bars 13 and 14 will now be described. Rotatably secured onthe shaft 40 is a lever thelower end 47 of which carries aroller whichrides on a cam 48 which is fixedly secured to the shaft 43. Connected tothe upper end 47 a of said lever is a pitman 49 which connects with-apin on a standard 50 which is secured to cross beam 24. Anchored to thestandard 50 is a cable 51 at the other end of which is a weight 52, thecable running over-a pulley 53. .The weight serves to hold the roller onlever arm 47 against its cam 48 and thus to cause i the one set ofsheet-supporting bars 13 to return after having been moved in onedirection by the cam 48 "ecured to the cross beam 25 for the other setof sheet-supporting bars 14 is a standard 54 corresponding to thestandard 50. Se-

cured to the standard'54 is a pitman 55 the other end of which issecured to one arni 56 of a lever which is rotatably mounted on the Ishaft 45. Projecting from the lever is an' arm 57 having a roller whichrides on the cam 48, the rollers on arms 57 and 47 engaging the cam 48at diametrically opposite points. An

chored to the lever arm 56 is a cable 58 at the other end of Which is aweight 59, the cable passing over pulleys 60an'd 61. The weight servesto hold the roller on arm 57 against its cam 48 and thus to cause theother set of sheet-supporting bars 14 to return after having been movedin onedirection by the cam 48. The weight of the mechanism supported bythe hangers 29 (29) serves to hold the rollers on the lever arm 41 (46)in engagement with the cam 42 as will be readily appreciated.- Othermechanism for imparting relative horizontal and vertical motions to thesheet-supporting bars may be employed.

Another important. feature of the invention is the arrangement formaintaining cool the under side of the conveyor mechanism and forpreventing ingress of air through the wall openings through which thecross beams 24 and 25 extend. The bottom or floor of the furnace isindicated at 62 and is considerably below the cross beams 24, 25, 24 and25*. Where the cross beams 24 and 25 project through the furnacechamberwalls. the furnace floor is extended laterally as indicated bynumeral 63. Walls 64 extend from the floor portion 63 above-the level ofthe arch 26 at the top of the opening through which the cross beams 24and 25project laterally of the furnace chamber side walls 10. In thebottom of the floor is shown a drain 65 and in the walls 64 are anoverflow pipe 66 and a furnace chamber is adapted to be filled withwater to 1 level which is above the top of said side openings of whichthe arch 26 forms the top and through which the cross beams 24 and 25project. The said openings are therefore sealed against the entry of airinto the furnace chamber there being no other openings in the furnacechamber walls through which air may enter. The level of the water is"such that all of the cross beams which support the rails 17 and'17 willbe immersed in the water and therefore kept cool.

The cam or power mechanism Ir ay be p0- sitioned in a compartment 68outside of the furnace chamber as shown. For simplicity of showing, Ihave shown the power mechanism for imparting horizontal and verticalmovement to the conveyer as at one side only of the furnace but it willbe understood that such mechanism may be duplicated at the other side ofthe furnace or appropriate connections for that purpose made with thesingle cam mechanism shown.

It will be obvious that changes may be made in size, shape andarrangement of the Various parts without departing from the spirit ofthe invention and I wish therefore that the showing shall be taken in asense diagrammatic.

\Vhatis claimed is:

1. In a heat-treating furnace, the combination of relatively movablesets of interdigitated work-supporting members for moving work throughthe furnace, ports extending crosswise through said members, burnerspositioned to direct hot combustion products through said ports, andmeans extending between said members below said ports for preventingflow of combustion products into a region below said members.

2. In a heat-treating furnace, the combination of interfingered membersfor moving work through the furnace, ports extending crosswise throughsaid members, burners firing into the furnace through said ports, andmeans movable with said members for pre venting entry of atmospheric airinto the furnace.

3. In a heat-treating furnace, the combination of two sets oflongitudinally extending and interdigitated work-supporting members eachset being movable, longitudinally spaced groups of ports extendingcrosswise through each of said sets in a manner to provide acontinuously open flow path for combustion gases, and burners arrangedto direct combustion gases through said ports, the burners beingpositioned in the opposite sidewalls of the furnace chamber in staggeredrelation whereby the flow of combustion gases through adjacent groups ofports is in opposite directions.

4. In a heat-treating furnace, the combination of movable members formoving work through the furnace, ports extending cross- 'wise throughsaid members, opposed burners at different levels, the burners at thelower level firing into the furnace through said ports and the upperlevel burner firing over said members.

5. In a heat-treating furnace, the combination of relatively movablesets of interdigifated work-supporting members for moving work throughthe furnace, ports extending crosswise through said members, mutuallyopposed burners at different levels, the lower level burner firing intosaid ports and the upper level burner firing over said members in theopposite direction, and means for directing combustion products from theoverfiring burner into the space initially traversed by the freshcombustion products from the burner which fires into said ports.

(5. In a heat-treating furnace,,the combina tion of relatively movablesets of interdigitated work-suppoizting members for moving work throughthe furnace, ports extending crosswise through said members, mutuallyopposed burners at diflerent levels, the lower level burners firing intosaid ports and the upper level burners firing over said members in theopposite direction, the furnace wall wherein the burner which fires intosaid ports is positioned being set back from the adjacentwork-supporting'member to provide a space for the inflow of combustionproducts from above said members to the entrance to said ports.

7. In a heat-treating furnace, the combination of relatively movablesets of interdigitated work-supporting members for moving work throughthe furnace, ports extending crosswise through both of said sets,burners positioned to tire into the furnace through said ports, veach ofsaid members comprising a longitudinally extending rail and a series ofrefractory blocks mounted on the rail, those blocks which are laterallyalined with the burners being provided with ports as aforesaid.

8. In a heat-treating furnace, the combination of a work-supporting bendof longitudinally extending railsarranged side by side for. relativevertical and longitudinal movement, a passage extending transverselythrough said bed, and means for projecting heating gases into thefurnace by way of said passage, the passage being formed by alined portsin said rails.

9. In a heat-treating furnace, the combination of a work-supporting bedof longitudinally extending rails arranged side by side for relativevertical and longitudinal movement, a plurality of passages extendingtransversely through said bed, burners firing into adjacent passagesfrom opposite directions, each passage being formed by alined ports insaid rails.

10. In a heat-treating furnace, the combination of a work-supporting bedof longitudinally extending rails arranged side by side for relativevertical and longitudinal movement, a passa e extending transverselythroughsaid bed, a burner firing into said passage, and means tending todirect gases from the furnace chamber into the stream of burner gasesentering said passage, said passage being formed by alined cross postsin said rails.

11. In combination, a heating chamber,

longitudinally extending interfingered members forming the hearth ofsaid chamber, movable means on which said members are supported andmeans carried by said members below the top thereof to forma movableseal tending to prevent free in-flow of air into the chamber from belowsaid members.

V 12. In combination, a heating chamber,

longitudinally extending interfingered mem- 2 bers forming the hearth ofsaid chamber,

movable means on which said members are supported, and means projectinglaterally from said member adjacent the bottom side thereof to formindividual seals between adjacent members to prevent'free passage oflgases from one side to the other ofsaid memers.

13. A method ofpassing relatively thin metal sheets through a heatingfurnace in a manner to prevent the sheets from bending on lines runningparallel with the direction of travel of the sheets comprisin impartingun dulatory form to the sheets during passage through the furnace, theundulations presenting a wave front transversely of the line of travelof the sheets.

1 A method of passing relatively thin metal sheets through a heatingfurnace in a manner to prevent the sheets from bending on 40 linesrunning parallel with the direction of travel of the sheets comprisingsupporting the sheets in such a manner that they as-' sume an undulatoryform transversely of the line of travel of the sheets.

In testimony whereof I aflix my si ature.

, RALF SMYTH COG AN.

